Create FungibleTokenMetadataViews contract

.github/workflows/ci.yml

@@ -9,7 +9,7 @@ jobs:
       - uses: actions/checkout@v2
       - uses: actions/setup-go@v2
         with:
-          go-version: '1.16.x'
+          go-version: '1.18.x'
       - uses: actions/cache@v1
         with:
           path: ~/go/pkg/mod
@@ -22,7 +22,7 @@ jobs:
           cache: 'npm'
           cache-dependency-path: lib/js/test/package-lock.json
       - name: Install Flow CLI
-        run: sh -ci "$(curl -fsSL https://raw.githubusercontent.com/onflow/flow-cli/master/install.sh)" -- v0.33.1-sc-m5
+        run: sh -ci "$(curl -fsSL https://raw.githubusercontent.com/onflow/flow-cli/master/install.sh)"
       - name: Flow cli Version
         run: flow version
       - name: Update PATH

README.md

@@ -115,7 +115,7 @@ Right now we are using unsigned 64-bit fixed point numbers `UFix64` as the type
 
 6 - Destroying a Vault
 
-If a `Vault` is explicitly destroyed using Cadence's `destroy` keyword, the balance of the destroyed vault must be subracted from the total supply.
+If a `Vault` is explicitly destroyed using Cadence's `destroy` keyword, the balance of the destroyed vault must be subtracted from the total supply.
 
 7 - Standard for Token Metadata
 
@@ -135,10 +135,60 @@ This spec covers much of the same ground that a spec like ERC-20 covers, but wit
 - Transfers can trigger actions because users can define custom `Receivers` to execute certain code when a token is sent.
 - Cadence integer types protect against overflow and underflow, so a `SafeMath`-equivalent library is not needed.
 
-### Metadata
+## FT Metadata
 
-A standard for token metadata is still an unsolved problem in the general blockchain world and we are still thinking about ways to solve it in Cadence. We hope to be able to store all metadata on-chain and are open to any ideas or feedback on how this could be implemented.
+FT Metadata is represented in a flexible and modular way using both the [standard proposed in FLIP-0636](https://github.com/onflow/flow/blob/master/flips/20210916-nft-metadata.md) and the [standard proposed in FLIP-1087](https://github.com/onflow/flips/blob/main/flips/20220811-fungible-tokens-metadata.md).
 
+When writing an NFT contract, you should implement the [`MetadataViews.Resolver`](contracts/utility/MetadataViews.cdc#L20-L23) interface, which allows your `Vault` resource to implement one or more metadata types called views.
+
+Views do not specify or require how to store your metadata, they only specify
+the format to query and return them, so projects can still be flexible with how they store their data.
+
+### Fungible token Metadata Views
+
+The [Example Token contract](contracts/ExampleToken.cdc) defines three new views that can used to communicate any fungible token information:
+
+1. `FTView` A view that wraps the two other views that actually contain the data.
+1. `FTDisplay` The view that contains all the information that will be needed by other dApps to display the fungible token: name, symbol, description, external URL, logos and links to social media.
+1. `FTVaultData` The view that can be used by other dApps to interact programmatically with the fungible token, providing the information about the public and private paths used by default by the token, the public and private linked types for exposing capabilities and the function for creating new empty vaults. You can use this view to [setup an account using the vault stored in other account without the need of importing the actual token contract.](transactions/setup_account_from_vault_reference.cdc)
+
+### How to implement metadata
+
+The [Example Token contract](contracts/ExampleToken.cdc) shows how to implement metadata views for fungible tokens.
+
+### How to read metadata
+
+In this repository you can find examples on how to read metadata, accessing the `ExampleToken` display (name, symbol, logos, etc.) and its vault data (paths, linked types and the method to create a new vault).
+
+First step will be to borrow a reference to the token's vault stored in some account:
+
+```cadence
+let vaultRef = account
+    .getCapability(ExampleToken.VaultPublicPath)
+    .borrow<&{MetadataViews.Resolver}>()
+    ?? panic("Could not borrow a reference to the vault resolver")
+```
+
+Latter using that reference you can call methods defined in the [Fungible Token Metadata Views contract](contracts/FungibleTokenMetadataViews.cdc) that will return you the structure containing the desired information:
+
+```cadence
+let ftView = FungibleTokenMetadataViews.getFTView(viewResolver: vaultRef)
+```
+
+Alternatively you could call directly the `resolveView(_ view: Type): AnyStruct?` method on the `ExampleToken.Vault`, but the `getFTView(viewResolver: &{MetadataViews.Resolver}): FTView`, `getFTDisplay(_ viewResolver: &{MetadataViews.Resolver}): FTDisplay?` and `getFTVaultData(_ viewResolver: &{MetadataViews.Resolver}): FTVaultData?` defined on the `FungibleMetadataViews` contract will ease the process of dealing with optional types when retrieving this views.
+
+Finally you can return the whole of structure or just log some values from the views depending on what you are aiming for:
+
+```cadence
+return ftView
+````
+
+```cadence
+/*
+When you retrieve a FTView both the FTDisplay and the FTVaultData views contained on it are optional values, meaning that the token could not be implementing then.
+*/
+log(ftView.ftDisplay!.symbol)
+```
 
 ## Bonus Features
 
@@ -171,14 +221,14 @@ A standard for token metadata is still an unsolved problem in the general blockc
 12 - Cloning the token to create a new token with the same distribution
 
 13 - Restricted ownership (For accredited investors and such)
-- whitelisting
-- blacklisting
+- allowlisting
+- denylisting
 
 # How to use the Fungible Token contract
 
 To use the Flow Token contract as is, you need to follow these steps:
 
-1. If you are using the Playground, you need to deploy the `FungibleToken` definition to account 1 yourself and import it in `ExampleToken`. It is a predeployed interface in the emulator, testnet, and mainnet and you can import definition from those accounts:
+1. If you are using the Playground, you need to deploy the `FungibleToken` definition to account 1 yourself and import it in `ExampleToken`. It is a pre-deployed interface in the emulator, testnet, and mainnet and you can import definition from those accounts:
     - `0xee82856bf20e2aa6` on emulator
     - `0x9a0766d93b6608b7` on testnet
     - `0xf233dcee88fe0abe` on mainnet
@@ -202,15 +252,15 @@ To use the Flow Token contract as is, you need to follow these steps:
 
  Users willing to use the Fungible Token Switchboard will need to setup their accounts by creating a new `FungibleTokenSwitchboard.Switchboard` resource and saving it to their accounts at the `FungibleTokenSwitchboard.StoragePath` path.
 
- This can be acomplished by executing the transaction found in this repository `transactions/switchboard/setup_account.cdc`. This transaction will create and save a Switchboard resource to the signer's account,
+ This can be accomplished by executing the transaction found in this repository `transactions/switchboard/setup_account.cdc`. This transaction will create and save a Switchboard resource to the signer's account,
  and it also will create the needed public capabilities to access it. After setting up their switchboard, in order to make it support receiving a certain token, users will need to add the desired token's receiver capability to their switchboard resource.
 
  ## Adding a new vault to the switchboard
  When a user wants to receive a new fungible token through their switchboard, they will need to add a new public capability linked to said FT to their switchboard resource. This can be accomplished in two different ways:
 
  1. Adding a single capability using `addNewVault(capability: Capability<&{FungibleToken.Receiver}>)`
     * Before calling this method on a transaction you should first retrieve the capability to the token's vault you are
-    willing to add to the switchboard, as is done in the template transaction `transactions/switchboard/add_vault_capabilty.cdc`.
+    willing to add to the switchboard, as is done in the template transaction `transactions/switchboard/add_vault_capability.cdc`.
 
     ```cadence
     transaction {
@@ -219,7 +269,7 @@ To use the Flow Token contract as is, you need to follow these steps:
 
         prepare(signer: AuthAccount) {
           // Get the example token vault capability from the signer's account
-          self.exampleTokenVaultCapabilty = 
+          self.exampleTokenVaultCapability = 
             signer.getCapability<&{FungibleToken.Receiver}>
                                     (ExampleToken.ReceiverPublicPath)
           // Get a reference to the signers switchboard
@@ -230,7 +280,7 @@ To use the Flow Token contract as is, you need to follow these steps:
 
         execute {
           // Add the capability to the switchboard using addNewVault method
-          self.switchboardRef.addNewVault(capability: self.exampleTokenVaultCapabilty)
+          self.switchboardRef.addNewVault(capability: self.exampleTokenVaultCapability)
         }
     }
     ```
@@ -279,7 +329,7 @@ This can be observed in the template transaction `transactions/switchboard/remov
 
     prepare(signer: AuthAccount) {
       // Get the example token vault capability from the signer's account
-      self.exampleTokenVaultCapabilty = signer.getCapability
+      self.exampleTokenVaultCapability = signer.getCapability
                     <&{FungibleToken.Receiver}>(ExampleToken.ReceiverPublicPath)
       // Get a reference to the signers switchboard  
       self.switchboardRef = signer.borrow<&FungibleTokenSwitchboard.Switchboard>
@@ -291,14 +341,14 @@ This can be observed in the template transaction `transactions/switchboard/remov
     execute {
       // Remove the capability from the switchboard using the 
       // removeVault method
-      self.switchboardRef.removeVault(capability: self.exampleTokenVaultCapabilty)
+      self.switchboardRef.removeVault(capability: self.exampleTokenVaultCapability)
     }
  }
  ```
  This function will panic if is not possible to `.borrow()` a reference to a `&{FungibleToken.Receiver}` from the passed capability.
 
- ## Transfering tokens through the switchboard
- The Fungible Token Switchboad provides two different ways of depositing tokens to it, using the `deposit(from: @FungibleToken.Vault)` method enforced by the `{FungibleToken.Receiver}` or using the `safeDeposit(from: @FungibleToken.Vault): @FungibleToken`:
+ ## Transferring tokens through the switchboard
+ The Fungible Token Switchboard provides two different ways of depositing tokens to it, using the `deposit(from: @FungibleToken.Vault)` method enforced by the `{FungibleToken.Receiver}` or using the `safeDeposit(from: @FungibleToken.Vault): @FungibleToken`:
 
  1. Using the first method will be just the same as depositing to `&{FungibleToken.Receiver}`. The path for the Switchboard receiver is defined in `FungibleTokenSwitchboard.ReceiverPublicPath`,
  the generic receiver path `/public/GenericFTReceiver` that can also be obtained from the NFT MetadataViews contract.
@@ -336,7 +386,7 @@ This can be observed in the template transaction `transactions/switchboard/remov
  }
  ```
 
- 2. The `safeDeposit(from: @FungibleToken.Vault): @FungibleToken` works in a similar way, with the difference that it will not panic if the desired FT Vault can not be obtained from the Switchboard. The method will return the passed vault, empty if the funds were deposited sucessfully or still containing the funds if the transfer of the funds was not possible. Keep in mind that when using this method on a transaction you will allways have to deal with the returned resource. An example of this can be found on `transactions/switchboard/safe_transfer_tokens.cdc`:
+ 2. The `safeDeposit(from: @FungibleToken.Vault): @FungibleToken` works in a similar way, with the difference that it will not panic if the desired FT Vault can not be obtained from the Switchboard. The method will return the passed vault, empty if the funds were deposited successfully or still containing the funds if the transfer of the funds was not possible. Keep in mind that when using this method on a transaction you will always have to deal with the returned resource. An example of this can be found on `transactions/switchboard/safe_transfer_tokens.cdc`:
  ```cadence
  transaction(to: Address, amount: UFix64) {
     // The reference to the vault from the payer's account